Lipid acyltransferases are known to be advantageous in food applications. Lipid acyltransferases have been found to have significant acyltransferase activity in foodstuffs. This activity has surprising beneficial applications in methods of preparing foodstuffs.
For instance, WO 2004/064537 discloses a method for the in situ production of an emulsifier by use of a lipid acyltransferase and the advantages associated therewith.
International Patent Application No. PCT/IB2001/000558 teaches the expression of lipid acyltransferases in (heterologous) host cell and is incorporated herein by reference.
The purpose of edible oil refining is to remove undesirable impurities that affect quality (taste, smell and appearance for example)) and storability.
Due to the wide variety of these impurities—free fatty acids, metal ions, colour compounds, odours, gums etc.—a series of processes of chemical and physical nature are conventionally employed for refining (see for example Bailey's Industrial Oil and Fat Products—2006 John Wiley & Sons—Sixth Edition).
Traditionally two processes have been used for degumming of oil which are the physical degumming and the chemical degumming processes.
In the so-called chemical refining, almost all free fatty acid content is removed by initial treatment with a large excess of NaOH. Also the phospholipids content is decreased to a phosphorus level typically below 10 ppm. The oil is subsequently bleached and deodorised.
The so-called physical refining generally consists of a water-degumming step followed by acid degumming, neutralisation, bleaching, steam stripping to remove free fatty acids and deodorisation.
Instead of using acid degumming during physical refinement developments were made to use enzymatic degumming.
The enzymatic degumming process was developed based on the use of pancreatic phospholipase. Because this enzyme was non-kosher the phospholipase was eventually substituted by a microbial phospholipase A1 (Lecitase Ultra™-Novozymes, Denmark) (Oil Mill Gazetteer, Vol 111 July 2005 pp 2-4).
The enzymatic process has several advantages over the chemical or the physical degumming processes including cost savings, higher yield and a more environmentally friendly process.
The enzymatic oil degumming process was based on the addition of a phospholipase to an oil which was already water degummed.
In WO2006/008508 lipid acyltransferases were taught for use in enzymatic degumming of edible oils. WO 2006/008508 teaches addition of a lipid acyltransferase to a water-degummed oil or the addition of a lipid acyltransferase to a crude oil without the need for the oil to undergo a water-degumming process.
“Water-degummed oil” may typically be obtained by a conventional “water degumming process” comprising mixing 1-2% w/w of hot soft water with warm (70-90° C.) crude oil (AOCS Introduction to the Processing of Fats and Oils—Table 8—Degumming Processes—http://www.aocs.org/meetings/education/mod3sample.pdf). A rule of thumb is that that amount of water added to crude oil is typically approximately equal to the amount of phospholipids in the crude oil. Usual treatment periods are 30-60 minutes. The water-degumming step removes the phosphatides and mucilaginous gums which become insoluble in the oil when hydrated. The hydrated phosphatides and gums can be separated from the oil by settling, filtration or centrifugation—centrifugation being the more prevalent practice. The essential object in said water-degumming process is to separate the hydrated phosphatides from the oil. The mixing of hot water into the oil, described above, should herein be understood broadly as mixing of an aqueous solution into the oil according to standard water-degumming procedures in the art.
In the conventional water degumming process the main part of the phosphatides are removed in a heavy gum phase. At the end of the water degumming process an oil phase is separated from a gum phase. Although the gum phase can be processed further into commercial products it is essentially viewed as a bi-product of oil refining. It is the oil phase which is commercially important. However, because the phosphatides can be good emulsifiers some oil is inevitably lost in the gum phase during water degumming. This leads to reduced yields of oil in the oil phase following water degumming.
With increases in oil prices and an increasing need for vegetable oil for biodiesel it is important to optimise the processing of edible oils for high oil yield.